1. Field of the Invention
The present invention relates generally to aircraft and more specifically to a vertical take-off and landing aircraft, which includes improved stability in hover flight over that of a helicopter.
2. Discussion of the Prior Art
The prior art provides several different types of vertical take-off and landing (VTOL) aircraft. One common VTOL method is that of a tilt-rotor design, where typically two larger propellers are mounted to the ends of an abbreviated wing that is designed to tilt the rotors from a vertical position to a horizontal position for normal flight. A drawback to this design is that there is an inherent “danger zone” of time, while the lift of the aircraft is reduced as its wings/propellers are rotated into the forward flight position. One example of the above challenge is encountered by the U.S. military's “Osprey” aircraft.
Another common VTOL method is known as redirected thrust. Although technically the same in terms of physics, these craft are usually powered by turbofan/jet engines, which produce tremendous amounts of directed thrust, which is then redirected downward for vertical take-off and tilted or redirected rearward to propel the plane into forward flight. The same danger of losing lift is present with the redirected thrust. However, the danger zone is greatly reduced, because of the horsepower to weight ratio. The best example of redirected thrust is the British military's AV8 Harrier fighter jet. The Harrier fighter jet is probably the most successful VTOL aircraft, except for the helicopter. Further, U.S. Pat. No. 5,890,441 to Swinson et al. discloses a horizontal and vertical take-off and landing unmanned aerial vehicle. The invention includes two vertical lift devices equally and longitudinally spaced from the center of gravity of the apparatus.
Accordingly, there is a clearly felt need in the art for a vertical take-off and landing aircraft, which does not have an inherent “danger zone” and provides improved stability in hover flight over that of a helicopter.